The invention relates to a combination containing a dough to be kept under refrigeration in a package and a process for its preparation.
WO 93/01724 patent application concerns already a process for preparing a yeast-leavened dough capable of being stored at refrigeration temperatures. This dough is prepared by mixing flour, water and yeast, packaging said dough in a container, which is a spirally wound composite can, sealing the container, proofing said dough in said container and storing said product at refrigeration temperatures.
The problem at the base of this patent is that during the storage, the yeasts which are used continue to grow and produce carbon dioxide. Then, after a period of storage of several weeks , the internal pressure in the container can be so high, that the container could explode. The reason of this pressure increase is the fact that for preparing the dough, they must make a proofing of the dough: when the yeasts has been highly activated for the step of proofing the dough, it is problematic to simply inactivate these yeasts by subjecting the obtained dough to a refrigeration temperature. In fact, these yeasts will probably not stop producing gas immediately by refrigeration,because their metabolism has been induced to produce much gas.
U.S. Pat. No. 1,904,741 concerns a packaging containing a dough prepared from a yeast. This packaging allows the dough to expand, but does not have a controlled atmosphere, so that it is not possible to have this dough stored for several weeks.
The present invention provides the possibility of delivering to the consumer an assembly containing a yeast-based dough, wherein the dough has been prepared and packed without any proofing a step.
The invention specifically concerns a combination of a dough product based on living yeast which generates gas over time, a closed packaging system for containing said dough product, the packaging system comprising a housing of a material which is essentially impervious to oxygen, valve means operatively associated with the housing for allowing exit of gas from the housing when the gas pressure exceeds a certain minimum value and which closes when said gas pressure drops below the minimum value to prevent entry of oxygen into the housing and a substantially oxygen-free atmosphere surrounding the dough.
The valve means used is called a one-way valve.
Under living yeast, we understand a yeast containing microorganisms which are still living during the storage.
Under refrigeration, we understand a dough to be kept at a temperature of below 12xc2x0 C., more particularly between 2 and 8xc2x0 C. The freezing point of the dough being under 0xc2x0 C., it is possible to keep this dough frozen at xe2x88x9218xc2x0 C. for at least 2 months.
According to the present invention, the dough does not have to be proofed and during the storage ,the dough is quickly saturated with gas, which allows to directly bake it without any proofing step. In fact, the presence of gas in the dough is sufficient to get the desired raising effect when the dough is baked.
The possible storage duration is of at least 4 weeks at 8xc2x0 C. and at least 3 weeks at 12xc2x0 C.
During storage at chilled temperature, as specified above, there is carbon dioxide also accumulating in the head space of the packaging. The presence on the packaging of the one-way valve will allow this carbon dioxide to escape from said packaging, however, so that only a small over pressure will build up internally. The overall quality of the dough is improved thanks to the release of the extra gas and other excess volatile compounds.
The small residual activity of the baker""s yeast during chilled storage has another important positive influence on the dough quality. It supplies at a constant slow rate precursor molecules that can develop the desired bread flavour upon baking of the dough. Since these flavour precursor molecules are unstable they cannot be produced in a single proofing step at ,theand beginning of the storage period as proposed by patent application WO 93/01724.
The type of the one-way valve which is used is not critical: we can use any valve on the market, for example from the Goglio type or the Raackmann type. The Goglio-type valve comprises valves from the company Bosch, Wipf and Wico. Both these types of valves will be explained in reference with FIGS. 4 and 5.
The advantage of the combination according to the invention is to make possible to use a more flexible packaging system and not a can as for the above mentioned WO patent application No. 93/01724.
The packaging system can be thermoformed or of the flow pack type. The material which is used is not critical. The important is that this material has a gas barrier property, to be sure that no oxygen enters the system.
In the case of thermoforming, we can use a base web (housing) which has to be thermoformed. We use for example the following composite sheets: A-PET/PE (amorphous polyester/polyethylene), PP/EVOH/PE (polypropylene/ethylene-vinyl alcohol copolymer/polyethylene) or PVC/PE (polyvinyl chloride/polyethylene).
This base web is more or less rigid, with a thickness comprised between 200 and 1000 microns. The top web has afterwards to be sealed on the thermoformed base web. This latter web, forming the cover for the package must have gas barrier and be heat stable. The material used can be chosen among the following materials: PA/PE(polyamide/polyethylene), OPA/PE (oriented polyamide/polyethylene) PET/PE (polyester/polyethylene) or OPP/PE (oriented polypropylene/polyethylene) which can have gas barriers in types of for example PVDC (polyvinylidene chloride), EVOH, metal or mineral layer. The thickness of the top web is comprised between 50 and 200 microns. Polyethylene has been chosen normally but any sealant which will give a sufficient adhesion between top and base web can be used.
In the case of a flow pack system, there is no obligation of rigidity. The material used is chosen among those which can be used as top webs in thermoforming. As for thermoforming we must use materials having gas barrier properties. The flow pack technique is described in xe2x80x9cL"" Emballage sous toutes ses facettesxe2x80x9d, 1988, Chapter 32.
The one-way valve is placed, in the case of thermoforming, on the top web, either on the inside or on the outside of the packaging, but preferably on the inside, to avoid therefore any risk of tearing said valve away.
In the case of a flow pack system, the one-way valve is disposed as on the top web of the thermoformed assembly.
The yeast can be of any type used in the bakery area. It is generally prefered that the species be the Saccharomyces genus. One particularly preferred species is S. Cerevisiae. 
The preferred baker""s yeast strains are of the lti (Low Temperature Inactive) type, for example those which are the object of European Patent Application 0487878 or most preferentially those described in a European Patent application filed by the same applicant :under the title xe2x80x9cLevure de boulangerie industrielle inactive au froidxe2x80x9d (No. 94104043.8). The lti baker""s yeast strains unify a very good characteristics in industrial cell mass production and drying with a very low gassing activity in refrigerated dough products up to 12xc2x0 C.
Yeast can be either in the fresh or dry form. In this latter case, the yeast has to be rehydrated just before use. The dough contains between 0.01 and 1% of yeast based on dry matter. In this specification, all the percentages are in weight.
The dough is obtained by mixing yeast, water, flour and other ingredients such as salt, sugars, oils or fats. In general, the dough is prepared for bakery products such as pizza, bread or french croissants. The oils or fats can be of vegetal or animal origin, for example butter fat or margarine. The flour can be of any type used in the bakery area. The presence of water binding agents, salt and/or sugar is useful for decreasing the water activity aw of the dough and for limiting the development of the natural microflora of the dough system.
Under substantially oxygen-free atmosphere, we understand an atmosphere with less than 1.5% oxygen, this atmosphere being nitrogen and carbon dioxide alone or in combination. The content of these gases can vary widely between 0 and 100%. For gases, the percentages are in volume. The fact of having a combination substantially oxygen-free is critical: this allows the possibility of having a long shelf-life and also to maintain a good texture of the dough after several weeks.
The dough in the packaging can be either in the form of blocks or in the form of rolled pieces ready to use for example as mentioned in European Patent Application No. 0158590.
For reasons of convenience for the consumer, it is preferred that the dough is protected with a cardboard. The type of cardboard is not critical, but must be a material compatible in the food area. The presence of this cardboard can also avoid a plugging of the one-way valve due to dough swelling. Also having the dough wrapped in a paper (separation paper, baking paper or other type of paper) can avoid any risk of plugging the one-way valve. Finally, it is preferred to have the one-way valve sufficiently spaced from said dough.
The invention further concerns a process for the preparation of the above mentioned combination wherein the dough is prepared by mixing a live yeast with at least water and flour, the dough is rolled or put into pieces and disposed in a packaging system, the one-way valve is applied on the packaging, the packaging is evacuated, gasflushed and sealed.
As already said above, we can use any yeast either in dry or in wet form, with the above mentioned concentrations.
The water is normally used at a temperature of below 16xc2x0 C., and it is preferred to use a part of the water in solid form, i.e. ice. The proportion of ice used is normally comprised between one and two parts of ice for six to ten parts of water.
The device used is a step-by-step device which will be explained in more detail in FIG. 6.
After the dough is put rolled or in pieces into the thermoformed packaging, the one-way valve is applied and the packaging is evacuated at a pressure between 0.07 and 0.01 bar. This step is necessary to evacuate the maximum of the oxygen, so that the content of this gas in the assembly is below 1.5%.
After the evacuation takes place, the gasflushing occurs with nitrogen and carbon dioxide alone or in combination. The amount of these gases introduced in the assembly is not critical, but it is preferably comprised between 40 and 80% of CO2.
After the sealing of the combination, the different combinations are cut into separate pieces and brought at a temperature of less than 8xc2x0 C. within a duration of less than 4 hours. This is necessary to guarantee a product having a shelf life at the above mentioned storage temperatures of at least 4 weeks.
The invention concerns further the dough which is kept under refrigeration. This dough contains between 43 and 62% of flour, between 5 and 23% fat, between ; 0.01 and 1% yeast, between 1.0 and 2.5% of sodium chloride or sugar, and between 23 and 33% of water.
The presence of sodium chloride or sugar is necessary for lowering the water activity. The flour used is already described above. The fat is a vegetable or animal fat, for example wheat gluten oil or margarine.
According to another embodiment, the dough contains furthermore between 0.5 and 1.5% of ethanol.
The invention relates finally to the system for the preparation of the combination of the invention comprising means for thermoforming the housing of the packaging, means for disposing the dough in the housing, means for delivering the top web with its one-way valve on the upper edge of the housing, means for gas flushing the inside of the packaging and sealing the top web on the upper edge and means for cutting each combination. As discussed above, the whole device operates in a step-by-step way.